Leonardo da Vinci’s Mona Lisa has been long studied and celebrated for its virtuosic composition and sfumato technique, its mysterious background and sitter, but two experimental psychologists in Germany are suggesting that the iconic painting may have another claim to fame: being the first 3D image in history.
In a paper published last year in the journal Perception and a follow-up forthcoming in the journal Leonardo, Claus-Christian Carbon and Vera M. Hesslinger posit that the original Mona Lisa (also known as “La Giocanda” in Italian) and a copy of it in the Prado could be two halves of a single stereoscopic image. To reach this conclusion, they began with the changed circumstances of the Prado picture: since the 18th century, it had featured a portrait of the Mona Lisa sitter, but against a black background. In 2012, Prado conservators removed the black overpainting to discover a background very similar to that of the Louvre painting. But the resemblance “is not limited to the superficial appearance,” the psychologists write in their Perception paper, continuing:
By comparison of the respective infrared reflectography results something interesting became visible: The genesis of the Louvre version is almost completely repeated in the Prado version, in fact from preparatory to upper paint layers; even specific corrections (e.g. of the position of the fingers) are present in the drawings of both portraits. This suggests that the person who painted the Prado version might actually have observed the complete creation of the original portrait “live.” Leonardo and the copyist might even have stood there together in the studio, painting simultaneously.
From there, Carbon and Hesslinger tracked the changes (“linear trajectories”) of some of the key features of the painting between the two versions and asked 32 participants to estimate the painter’s and model’s relative positions in both works. What they found was
… a difference between the paintings that reflects a disparity value Δ = 69.3 mm … Interestingly, this is only slightly … above the average inter-ocular distance of Italian males (i.e., 64.1 mm, see Farkas et al 2005). The two Mona Lisas, it seems, were executed under spacial conditions that mimic human binocular vision.
In last year’s Perception paper, the psychologists push the theory that Leonardo, who was also a mathematician, engineer, and inventor, was actively attempting to create some kind of stereoscopic image, more than 300 years before Sir Charles Wheatstone invented the stereoscope. But in the forthcoming follow-up study — which mostly focuses on the question of the Mona Lisa’s landscape background and whether or not it was a motif from Leonardo’s studio (their answer: yes) — Carbon and Hesslinger leave the question more open, conceding that “whether this was or was not intended by Leonardo is debatable indeed.”
Still, they contend that the Mona Lisa has “obvious stereoscopic qualities” either way, and conclude by making a case for something that seems increasingly popular these days: using “methods from mathematics and natural sciences [to] enrich aesthetic and (art) history research,” what they call a “joint ‘new science of aesthetics.'”